Pimentos are a variety of red bell peppers. You'd have to allow a green bell pepper to stay on the plant long enough to turn red to be used as a substitute for a pimento.

To can: Select ripe peppers; place in boiling water for 12-15 minutes or hot oven for 6-8 minutes. Place in cold water, core, peel, flatten in layers in canning jars to within 1/2 inch of top. Process pints at 10 lbs pressure for 10 minutes. Do not add oil to peppers, but you may add a bit of boiling water to jar before sealing.